PT - JOURNAL ARTICLE
AU - Schiffer, Michele
AU - Hangartner, Sandra
AU - Hoffmann, Ary A.
TI - Assessing the relative importance of environmental effects, carry-over effects and species differences in thermal stress resistance: a comparison of Drosophilids across field and laboratory generations
DP - 2013 Jan 01
TA - The Journal of Experimental Biology
4099 - http://jeb.biologists.org/content/early/2013/06/27/jeb.085126.short
4100 - http://jeb.biologists.org/content/early/2013/06/27/jeb.085126.full
AB - There is increasing interest in comparing species of related organisms for their susceptibility to thermal extremes in order to evaluate potential vulnerability to climate change. Comparisons are typically undertaken on individuals collected from the field with or without a period of acclimation. However this approach does not allow the potential contributions of environmental and carry-over effects across generations to be separated from inherent species differences in susceptibility. To assess the importance of these different sources of variation, we here consider heat and cold resistance in Drosophilid species from tropical and temperate sites in the field and across two laboratory generations. Resistance in field-collected individuals tended to be lower when compared to F1 and F2 laboratory generations, and species differences in field flies were only weakly correlated to differences established under controlled rearing conditions, unlike in F1 - F2 comparisons. This reflected large environmental effects on resistance associated with different sites and conditions experienced within sites. For the cold recovery assay (after 8 h cold stress) there was no strong evidence of carry-over effects, whereas for the heat knockdown (heat) and cold recovery assays (after 2 h cold stress) there was some evidence for such effects. However for heat these were species-specific in direction. Variance components for inherent species differences were substantial for resistance to heat and 8 h cold stress, but small for 2 h cold stress, though this may be a reflection of the species being considered in the comparisons. These findings highlight that inherent differences among species are difficult to characterize accurately without controlling for environmental sources of variation and carry-over effects. Moreover they also emphasize the complex nature of carry-over effects that depend on the nature of stress traits and the species being evaluated.